A technique has been developed for measuring the properties of discharge-based plasma channels by monitoring the centroid location of a laser beam exiting the channel as a function of input alignment offset between the laser and the channel. Experiments were performed using low-intensity (< 1014 Wcm-2) laser pulses focused onto the entrance of a hydrogen-filled capillary discharge waveguide. Scanning the laser centroid position at the input of the channel and recording the exit position allows determination of the channel depth with an accuracy of a few percent, measurement of the transverse channel shape, and inference of the matched spot size. In addition, accurate alignment of the laser beam through the plasma channel is provided by minimizing laser centroid motion at the channel exit as the channel depth is scanned either by scanning the plasma density or the discharge timing. The improvement in alignment accuracy provided by this technique will be crucial for minimizing electron beam pointing errors in laser plasma accelerators.

Density perturbations in a hydrogen-filled capillary discharge waveguide have been used to control the injection of electrons into a laser wakefield. This has allowed injection and acceleration in channels of lower density than previously possible, and the production of relativistic electron beams with improved stability. For parameters of optimum stability, the mean bunch energy was 300MeV +- 7 MeV rms, with divergence 1.3 mrad +- 0:1 mrad rms and pointing stability 0.8 mrad rms.

This dissertation examines how multiple understandings of gender variance have come to be articulated through the category Transgender. Whereas prior studies have focused on the emergence of categories in a particular place, compared categorization across national contexts, or examined global convergence resulting from the “diffusion” of Western culture to other parts of the world, I focus on the contention between “transgender” and other modes of understanding gender variance. Conceptualizing transnational movement as “circulation,” I illuminate the mechanisms through which categories and their meanings transform as they move. Drawing from interview, archival, and participant observation data, I trace the transnational circulation of Transgender in three key, interacting arenas: the United Nations (UN), international non-governmental organizations (INGOs), and the international biomedical field. The first part of the dissertation traces the emergence of Transgender in the West. I analyze how shifts in medical science, queer and feminist theory, and a broader turn to self-identification created the discursive preconditions for “transgender” to emerge as a social category in the second half of the 20th century. In medical discourse and feminist and queer theory, I argue, Transgender came to comprise three parts: a gender identity, a dissonance from sex assigned at birth, and an ontological distinction between gender identity and sexual orientation. The rest of the dissertation examines how the Western category Transgender circulates transnationally in the 21st century. I find an initial convergence around the three-part definition of Transgender in early INGO and UN reports, conferences, and medical journal articles. Yet, the would-be umbrella category must contend with multiple modes of understanding gender variance. INGO staff, UN bureaucrats and biomedical scientists, whom I refer to as “gender experts,” attempt to deal with these divergences and maintain the global relevance of Transgender. Opposition from some country officials and UN Agency bureaucrats leads UN gender experts to “slip in” Transgender in incoherent ways. In INGOs, on the other hand, gender experts successfully deploy “containment strategies” to universalize Transgender. These strategies simultaneously transform the category itself. By focusing on categories as analytic objects, conceptualizing movement as circulation rather than diffusion, and attending to multiplicity in modes of understanding, the dissertation illuminates the spatial contingency and dynamism of a putatively global category. Analyzing the emergence and transformation of Transgender, moreover, reveals the inextricability of complex configurations of gender, sex, and sexual desire and the relationship between identity and practice.